A small, roundish object or piece of something; pellet; grain

to gather every single grain of the harvest into the granary

One bad person or thing ruins everything else, like a single piece of rat droppings spoiling an entire pot of soup.

Literally "one pellet of rat feces spoiled the whole pot of congee"; used to describe how a single small negative element can ruin an entire situation or group.

(biology) A small membrane-bound storage container within a cell that holds substances to be released outside the cell

atmospheric particulate matter with a diameter of less than 2.5 micrometers that can enter the lungs

Tiny particles floating in the air that can be inhaled into the human respiratory system; a major air pollutant typically under 10 micrometers in diameter.

The total amount of solid or liquid particles suspended in the air or water that do not easily settle; its concentration in the air is a key indicator for monitoring air quality.

Fine air pollutants consisting of particles with a diameter of 2.5 micrometers or less; a key indicator of air quality also known as PM2.5.

Bricks made of mud reinforced with grass; earth clods with grass growing on them

Not a single grain was harvested; describes a total crop failure due to disaster or bad weather.

micro-particles or particulate matter (PM)

Masses of solid particles larger than one micron, often produced by fuel combustion or industrial processes, and a major source of air pollution

type of small neuron found in the brain, particularly in the cerebellum and olfactory bulb